The width of a standard, manual, adult-sized wheelchair is 26 inches at the rear wheels, according to the Americans with Disabilities Act website. The width between each footrest is 18 inches.
The seat width of a standard adult wheelchair ranges between 16 and 20 inches, while the width of an extra-wide wheelchair ranges between 20 and 24 inches, states About.com. Standard wheelchairs are for individuals weighing less than 300 pounds. Extra-wide wheelchairs are for those weighing over 300 pounds.
Pediatric wheelchairs have a narrower seat and are 14 inches wide, notes About.com. These chairs are for children and those who have smaller frames. These wheelchairs have a maximum weight limit of 250 pounds.